1. Field of the Invention
The present invention relates to web processing machines, particularly to semi-rotary web processing machines.
2. Background Art
Web processing machines using a rotating tool cylinder processing successive sections of a continuous web of material include for example machine performing die cutting, laminating, stamping, printing, and coating. The successive sections are usually identical (i.e. repeats), and can be for example shapes to be cut, printed images, etc. The rotating tool is usually required to have the same tangential speed as the linear speed of the web when the tool is used to process each section of the web.
When the speed of the tool cylinder rotation and of the web are constant, the length of one section of web to be processed is usually equal to the circumference of the tool cylinder. As such, changing the length of the sections usually implies changing the tool cylinder. To reduce costs, a number of semi-rotary processes have emerged, allowing the use of a single tool cylinder for various sizes of web section. In most cases however, the modules performing the semi-rotary process cannot be used in series with other modules, since the web exiting the module usually travels at an intermittent speed, and as such is not compatible with a rotary process.
In web processing it is often desirable to perform multiple operations on a web, for example printing, laminating and cutting, through the use of several modules, one per operation to be performed, installed in series, i.e. with the web circulating through the modules and from one to the other in a continuous fashion. However, in such series the modules are usually dependent on one another for maintaining the web in tension, and as such a registry error at one module is reflected in all the downstream modules. As such, registry of the web at each module can be a complex procedure, usually done through modifying the speed or position of the multiple tool cylinders.